156 TEE POPULAR SCIENCE MONTHLY 



can penetrate the shell, especially if the shell is moist. These bacteria 

 find excellent food in eggs and will multiply at an enormous rate unless 

 the eggs are kept cold. The producer usually brings the eggs once a 

 week to the country store, where they remain for another week or two 

 before being delivered to a factory for desiccation. When we consider 

 that one bacterium may have a progeny of 17 millions in 24 hours under 

 favorable food and temperature conditions, it is not surprising to find 

 that eggs used for desiccation contain millions of microorganisms. Bad 

 eggs are usually recognized by holding them up to a bright light in a 

 dark room, a process known as " candling." This will reveal dark spots 

 resulting from bacterial multiplication, or colonies of molds, or em- 

 bryonic development of the chick. But we must remember that mil- 

 lions of bacteria take up a smaller space than the head of a pin, so that 

 the process of candling will show their presence only after enormous 

 multiplication has taken place. On the other hand, if fresh eggs are 

 desiccated within a few hours or a day after laying and have been kept 

 cold during this interval, the final product will contain about the same 

 number of bacteria as the original eggs. It must not be assumed, how- 

 ever, that the presence of many millions of bacteria is necessarily in- 

 jurious to health. Of all species of bacteria known to science an ex- 

 ceedingly small number is injurious, and these are rarely found in eggs. 



CONSERVATION" BY COLD STORAGE 



The present methods of cold storage are the natural result of evo- 

 lution from the practise of using the cellars of farmers and produce 

 dealers. Surplus food material is stored in warehouses, where it will 

 keep in good condition for various periods of time, these periods de- 

 pending largely upon the degree of temperature maintained. Such 

 storage makes possible an artificial season, which may be long enough 

 to bridge the gap between one producing season and the next. The im- 

 portance of this can not be overestimated and has found expression in 

 the fact that the Canadian government is subsidizing cold-storage 

 plants. 



The degree of temperature to which foods are exposed in cold stor- 

 age varies according to the nature of the food. Fruits, vegetables and 

 and shell eggs are permanently injured by freezing and are therefore 

 kept just above the freezing point. If eggs are broken, the yolks and 

 whites mixed and then frozen, they can be preserved for a long time. 

 What has been said about desiccated eggs applies with equal force to 

 frozen and cold storage eggs. If they are in good condition when placed 

 in cold storage or when broken for freezing they will keep for a long 

 time. Usually considerable deterioration takes place before they reach 

 the packer. Especially is this true of summer eggs. April and May 

 eggs, if placed in cold storage in good condition, are of better quality 



